1. Field of the Invention
The present invention relates to an image processing apparatus and an image processing method which aims to obtain output images with high quality. More particularly, it relates to an image processing apparatus and an image processing method which conduct different resolution conversion processing for each scanning direction.
2. Description of Related Art
There has been known image processing technology to enhance resolution of input image data, which aims to obtain output images with high quality. As an example of image processing technology of this kind, U.S. Pat. No. 5,751,929 discloses image processing to enhance resolution in only one scanning direction (a main-scanning direction, for example). As another example of that, the JP Laid-open Patent Publication No. 10-229493 discloses a manner to enhance resolution, wherein region discrimination of image data is conducted in accordance with two-dimensional pattern matching and printing position of the output image is adjusted in accordance with the discrimination result.
However, in the above-mentioned image processing technology, it was not feasible to conduct different manners of resolution conversion processing depending on scanning direction. For example, this kind of difficulty holds true in an image such that is an edge region in a main-scanning direction while a non-edge region in a sub-scanning direction, i.e., a character image continuously changing its density, or the like. Therefore, there have been some difficulties to obtain a high-quality output image depending on type of image. Such difficulties arise because conventional image processing technology applies multi-gradation expression relying on area gradation such as pulse duration modulation and because resolution conversion processing is basically conducted in a one-dimensional direction.